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The Assessment of Radionuclide Retardation in Fractured Crystalline Rocks

Published online by Cambridge University Press:  10 February 2011

W. Russell Alexander
Affiliation:
GGWW (Rock-Water Interaction Group), Institutes of Geology and of Mineralogy and Petrology, University of Berne, Baltzerstrasse 1, 3012 Bern, Switzerland
Kunio Ota
Affiliation:
PNC (Power Reactor and Nuclear Fuel Development Corporation), Tono Geoscience Centre, 959-31 Jorinji, Toki, Gifu 509-51, Japan. ([email protected])
Bernhard Frieg
Affiliation:
Nagra (Swiss National Co-operative for the Disposal of Radioactive Waste), Hardstrasse 73, 5430 Wettingen, Switzerland
Ian G. Mckinley
Affiliation:
Nagra (Swiss National Co-operative for the Disposal of Radioactive Waste), Hardstrasse 73, 5430 Wettingen, Switzerland
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Abstract

The joint Nagra/PNC Radionuclide Migration Programme has been running for over ten years in Nagra‘s Grimsel Test Site in the central Swiss Alps. The programme is specifically aimed at the further development of conceptual models of radionuclide transport in the geosphere, rigorously testing the applicability of current transport codes to quantify radionuclide migration in situ and assessing how successfully laboratory sorption data (specifically, Kd values) may be extrapolated to in situ conditions to predict radionuclide retardation in the geosphere [1]. A large series of field tracer migration experiments was carried out in a hydrologically well characterised water-bearing, complex fracture (or shear zone), increasing in complexity from simple, nonsorbing fluoresceine (a fluorescent dye), 3H, 3,4He, 82Br and 123I through weakly sorbing 22.24Na,85Sr and 86Rb to a final, long-term experiment with moderately sorbing 134,137Cs. The radionuclides were injected into a dipole flow field where the flowpath length, dipole width or shape and groundwater flow velocity were all varied. After a considerable learning period, generally good fits could be obtained between transport code predictions and subsequent field tracer breakthrough curves, suggesting that the transport codes tested were a reasonable representation of in situ conditions.

Type
Research Article
Copyright
Copyright © Materials Research Society 1998

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References

REFERENCES

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